Many materials undergo a change in state as a result of a "curing reaction." For example, as a result of a curing reaction a liquid resin composition can be changed into a solid or elastomeric material. The curing reaction can be initiated in a number of different ways, including for example, heating the uncured sample, mixing two or more reactive components together, or exposing the uncured material to an activating radiation source or electron beam energy. Depending on the method of curing employed the transition time between states can vary in length. For some materials the change in state may be observed by simply probing the material and observing a change in viscosity. This technique, however, is subject to error and misinterpretation in many cases. In addition, manually probing samples may damage the sample, and may not indicate small but important changes in the extent of cure. Other techniques of observing a material's change in state include monitoring the rheological properties of the material, or analytically monitoring the material (e.g., using an instrument such as an NMR probe to observe directly a change in the functional groups of the material). Unfortunately, these direct techniques are often not practical for the routine monitoring of a cure reaction or may be invasive or destructive of the sample being monitored.
One example of a material that undergoes a curing reaction is a silicone material. "Silicones" are synthetic polymeric materials that possess an extraordinarily wide range of physical properties. They can be low- or high-viscosity liquids, solid resins, or vulcanizable gums. They display an unusual combination of organic and inorganic chemical properties that are due to their unique molecular structure of alternating silicon and oxygen atoms. One typical polysiloxane polymer is depicted below in formula F1. ##STR1## These silicone polymers may be made by an equilibrium process from other siloxanes and typically range in viscosity from about 0.01 Pa s to 2500 Pa s. Silicone polymers can be mixed with other chemicals and fillers into an enormous variety of products that serve in a multitude of applications.
Vulcanizing silicones are a special class of silicones that have as a common attribute the development of a "crosslinked" elastomer from relatively low molecular weight polymers by means of a chemical reaction that forms these crosslinks and effectively extends chain length simultaneously. Vulcanizing silicones (e.g., addition-cure silicones) have many applications in industry including use as sealants, caulks, adhesives, coatings, potting materials, release liners, otologic impression materials, molding materials, dental impression materials and medical and dental implants. An essential ingredient in a vulcanizing silicone is a crosslinking component (hereinafter the "crosslinker") that reacts with the "functional group" or groups (e.g., R.sup.1 and R.sup.2 of figure F1) of the polymer chains to simultaneously lengthen them and connect them laterally to form the crosslinked network characteristic of a silicone elastomer. Usually a catalytic agent is included to facilitate the reaction of the crosslinker with the polymer's functional groups.
There are many types of vulcanizing silicones and likewise many types of crosslinking components and catalysts. Two such systems include (i) condensation-cured silicones and (ii) addition-cured, e.g., hydrosilylation cured (alternatively spelled "hydrosilation") silicones. Condensation-cured silicones characteristically, and in many instances detrimentally, release water (or alcohol) as a by-product of the crosslinking reaction. The crosslinking reaction in these systems is triggered typically by combining the silicone polymer, the crosslinker and the catalyst. A variety of catalysts initiate and accelerate condensation curing such as amines and carboxylic acid salts of tin. At low temperatures the condensation-cured silicone typically requires long times to fully cure (hours or even days). Higher catalyst concentrations and/or higher temperatures can shorten the cure time.
Addition-cured silicones (e.g., hydrosilylation cured silicones) are generally considered to be of higher quality and are dimensionally more accurate than condensation-cured silicones. Unlike condensation-cured silicones, addition-cured silicones, e.g., hydrosilation-cured silicones, do not produce detrimental byproducts during curing. Such silicones differ from condensation-cured silicones in that the hydrosilation-cured composition typically contains:
(1) a polymer which contains two or more vinyl functional groups; PA1 (2) a "hydrosilane" crosslinker component containing two or more SiH bonds; and PA1 (3) a precious metal catalyst such as a platinum catalyst. PA1 (a) organohydrosilanes having the empirical formula, EQU (H).sub.a (R.sup.3).sub.b Si.sub.c (F 2) PA1 (b) organohydrocyclopolysiloxanes having the empirical formula, EQU H.sub.d R.sup.3.sub.e (SiO).sub.f (F 3) PA1 (c) organohydropolysiloxane polymers or copolymers having the empirical formula, EQU (H).sub.g (R.sup.3).sub.h Si.sub.j O.sub.(j-1) (F 4) PA1 (a) unsaturated silanes having the empirical formula, EQU R.sub.a R'.sub.b Si.sub.c X.sub.z (F 6) PA1 (b) unsaturated linear or branched siloxanes of the empirical formula, EQU R.sub.d R'.sub.e Si.sub.f O.sub.(f-1) (F 7) PA1 (c) unsaturated cyclic siloxanes of the empirical formula, EQU R.sub.d R'.sub.e Si.sub.f O.sub.f (F 8) PA1 A is O, S, or NR.sup.22, wherein PA1 R.sup.22 is hydrogen, a hydrocarbyl-containing group, or a heterocyclic group, preferably R.sup.22 is a group selected from the group consisting of: hydrogen, a C.sub.1 -C.sub.20 alkyl, a C.sub.3 -C.sub.18 cycloalkyl, a C.sub.6 -C.sub.18 aryl, a C.sub.2 -C.sub.18 alkenyl, a C.sub.6 -C.sub.18 arylamino, and substituted sulfonyl; more preferably R.sup.22 is selected from the group consisting of hydrogen and --SO.sub.2 C.sub.6 H.sub.5 ; and PA1 B is any group capable of providing extended conjugation thereby rendering the dye capable of absorbing visible, near-UV, or near-infrared radiation including groups of formula D, E, F, H, or J, wherein PA1 D is represented by formula (F12): ##STR7## wherein: each R.sup.5, R.sup.6, R.sup.7, R.sup.8, and R.sup.9 group is independently hydrogen, halogen, a hydrocarbyl-containing group, or a heterocyclic group, preferably each R.sup.5, R.sup.6, R.sup.7, R.sup.8, and R.sup.9 group is independently selected from the group consisting of: hydrogen, halogen, a C.sub.1 -C.sub.20 alkyl, a C.sub.1 -C.sub.20 alkoxy, a C.sub.3 -C.sub.18 cycloalkyl, a C.sub.6 -C.sub.18 aryl, a C.sub.6 -C.sub.18 aryloxy, a C.sub.6 -C.sub.18 hydroxyaryl, a C.sub.6 -C.sub.18 arylcarboxy, a C.sub.6 -C.sub.18 carboxyaryl, a C.sub.2 -C.sub.18 is alkenyl, a C.sub.1 -C.sub.20 alkylamino, a C.sub.6 -C.sub.18 is arylamino, a C.sub.6 -C.sub.18 aminoaryl, a C.sub.2 -C.sub.20 di(hydrocarbyl)amino, morpholino, and alkylamido and wherein any two adjacent R.sup.5, R.sup.6, R.sup.7, R.sup.8, and R.sup.9 groups may be connected to form a saturated or unsaturated ring, for example, R.sup.5 and R.sup.6 or R.sup.6 and R.sup.7 may be joined by or be a --C.sub.4 H.sub.4 -- or --C.sub.3 H.sub.3 N-- moiety; more preferably each R.sup.5, R.sup.6, R.sup.7, R.sup.8 and R.sup.9 group is independently selected from the group consisting of: hydrogen, halogen, a C.sub.1 -C.sub.10 alkyl, a C.sub.1 -C.sub.10 alkoxy, a C.sub.5 -C.sub.8 cycloalkyl, a C.sub.6 -C.sub.10 aryl, a C.sub.6 -C.sub.18 aryloxy, a C.sub.2 -C.sub.10 alkenyl, a C.sub.1 -C.sub.10 alkylamino, a C.sub.6 -C.sub.18 arylamino, a C.sub.2 -C.sub.20 di(hydrocarbyl)amino, morpholino, and alkylamido and wherein any two adjacent R.sup.5, R.sup.6, R.sup.7, R.sup.8, and R.sup.9 groups may be connected to form a saturated or unsaturated 5 or 6 member ring; most preferably each R.sup.5, R.sup.6, R.sup.7, R.sup.8 and R.sup.9 group is independently selected from the group consisting of: hydrogen, methyl, ethyl, propyl, butyl, methoxy, ethoxy, propoxy, a C.sub.5 -C.sub.8 cycloalkyl, a C.sub.6 -C.sub.10 aryl, benzyloxy, naphthyloxy, a C.sub.2 -C.sub.10 alkenyl, N,N-dialkylamino, N-alkyl-N-arylamino, --N(Et)[((CH.sub.3).sub.3 C).sub.2 (CH.sub.3).sub.1 SiOCH.sub.2 CH.sub.2 ], chlorine, bromine, morpholino, and alkylamido and wherein R.sup.5 and R.sup.6 or R.sup.6 and R.sup.7 may be joined by or be a --C.sub.4 H.sub.4 --, --(CH.sub.2).sub.3 --, or --C.sub.3 H.sub.3 N-- moiety; PA1 E is represented by formula (F13): ##STR8## wherein: X.sup.1 is C(R.sup.12).sub.2, S, NR.sup.12, or O, more preferably X.sup.1 is S or O, most preferably X.sup.1 is S; PA1 X.sup.2 is C(R.sup.12).sub.2, S, NR.sup.12, or O, more preferably X.sup.2 is C(R.sup.12).sub.2 or NR.sup.12, most preferably X.sup.2 is NR.sup.12 ; and PA1 each R.sup.10, R.sup.11 and R.sup.12 group is independently hydrogen, a hydrocarbyl-containing group, or a heterocyclic group, preferably each R.sup.10, R.sup.11 and R.sup.12 group is independently selected from the group consisting of: hydrogen, a C.sub.1 -C.sub.20 alkyl, a C.sub.1 -C.sub.20 alkoxy, a C.sub.3 -C.sub.18 cycloalkyl, a C.sub.6 -C.sub.18 aryl, a C.sub.6 -C.sub.18 aryloxy, a C.sub.6 -C.sub.18 hydroxyaryl, a C.sub.6 -C.sub.18 arylcarboxy, a C.sub.6 -C.sub.18 carboxyaryl, a C.sub.2 -C.sub.18 alkenyl, a C.sub.1 -C.sub.20 alkylamino, a C.sub.6 -C.sub.18 arylamino, a C.sub.6 -C.sub.18 aminoaryl, a C.sub.2 -C.sub.20 di(hydrocarbyl)amino, and wherein R.sup.10 and R.sup.11 may be connected to form or be a ring; more preferably each R.sup.10, R.sup.11 and R.sup.12 group is independently selected from the group consisting of: hydrogen, a C.sub.1 -C.sub.10 alkyl, a C.sub.1 -C.sub.10 alkoxy, a C.sub.5 -C.sub.8 cycloalkyl, a C.sub.6 -C.sub.10 aryl, a C.sub.2 -C.sub.10 alkenyl, and a C.sub.1 -C.sub.10 alkylamino, and wherein R.sup.10 and R.sup.11 may be connected to form or be a ring; and most preferably each R.sup.10, R.sup.11 and R.sup.12 group is independently selected from the group consisting of: hydrogen, methyl, ethyl, propyl, butyl, methoxy, ethoxy, propoxy, a C.sub.5 -C.sub.8 cycloalkyl, a C.sub.6 -C.sub.10 aryl, a C.sub.2 -C.sub.10 alkenyl, a C.sub.1 -C.sub.10 alkylamino, chlorine, and bromine, and wherein any two adjacent R.sup.10, R.sup.11, and R.sup.12 groups may be joined by or be a --C.sub.4 H.sub.4 --, --(CH.sub.2).sub.3 --, or --C.sub.3 H.sub.3 N-- moiety; PA1 F is represented by formula (F14): ##STR9## wherein: X.sup.3 is N or CR.sup.16 ; and PA1 each R.sup.13, R.sup.14, R.sup.15, and R.sup.16 group is independently hydrogen, halogen, a hydrocarbyl-containing group, or a heterocyclic group and wherein any two adjacent R.sup.13, R.sup.14, R.sup.15, and R.sup.16 groups may be connected to form a ring, preferably each R.sup.13, R.sup.14, R.sup.15, and R.sup.16 group is independently selected from the group consisting of: hydrogen, halogen, a C.sub.1 -C.sub.20 alkyl, a C.sub.1 -C.sub.20 alkoxy, a C.sub.3 -C.sub.18 cycloalkyl, a C.sub.6 -C.sub.18 aryl, a C.sub.6 -C.sub.18 aryloxy, a C.sub.6 -C.sub.18 hydroxyaryl, a C.sub.6 -C.sub.18 arylcarboxy, a C.sub.6 -C.sub.18 carboxyaryl, a C.sub.2 -C.sub.18 alkenyl, a C.sub.1 -C.sub.20 alkylamino, a C.sub.6 -C.sub.18 arylamino, a C.sub.6 -C.sub.18 aminoaryl, a C.sub.2 -C.sub.20 di(hydrocarbyl)amino and wherein any two adjacent R.sup.13, R.sup.14, R.sup.15, and R.sup.16 groups may be connected to form a ring; more preferably each R.sup.13, R.sup.14, R.sup.15 and R.sup.16 group is independently selected from the group consisting of: hydrogen, halogen, a C.sub.1 -C.sub.10 alkyl, a C.sub.1 -C.sub.10 alkoxy, a C.sub.5 -C.sub.8 cycloalkyl, a C.sub.6 -C.sub.10 aryl, and a C.sub.2 -C.sub.10 alkenyl; and most preferably each R.sup.13, R.sup.14, R.sup.15, and R.sup.16 group is independently selected from the group consisting of: hydrogen, methyl, ethyl, propyl, butyl, methoxy, ethoxy, propoxy, a C.sub.5 -C.sub.8 cycloalkyl, and phenyl; PA1 H is represented by formula (F16): ##STR10## wherein: each R.sup.20 and R.sup.21 group is independently hydrogen, halogen, a hydrocarbyl-containing group, or a heterocyclic group and wherein R.sup.20 and R.sup.21 may be connected to form a ring, preferably each R.sup.20 and R.sup.21 group is independently selected from the group consisting of: hydrogen, halogen, a C.sub.1 -C.sub.20 alkyl, a C.sub.1 -C.sub.20 alkoxy, a C.sub.3 -C.sub.18 cycloalkyl, a C.sub.6 -C.sub.18 aryl, a C.sub.6 -C.sub.18 aryloxy, a C.sub.6 -C.sub.18 hydroxyaryl, a C.sub.6 -C.sub.18 arylcarboxy, a C.sub.6 -C.sub.18 carboxyaryl, a C.sub.2 -C.sub.18 alkenyl, a C.sub.1 -C.sub.20 alkylamino, a C.sub.6 -C.sub.18 arylamino, a C.sub.6 -C.sub.18 aminoaryl, a C.sub.2 -C.sub.20 di(hydrocarbyl)amino, morpholino, and furyl and wherein R.sup.20 and R.sup.21 may be connected to form or be a saturated or unsaturated ring; more preferably each R.sup.20 and R.sup.21 group is independently selected from the group consisting of: hydrogen, halogen, a C.sub.1 -C.sub.10 alkyl, a C.sub.1 -C.sub.10 alkoxy, a C.sub.5 -C.sub.8 cycloalkyl, a C.sub.6 -C.sub.10 aryl, a C.sub.6 -C.sub.10 aryloxy, a C.sub.2 -C.sub.10 alkenyl, a C.sub.1 -C.sub.10 alkylamino, a C.sub.6 -C.sub.18 arylamino, and 2-furyl; and most preferably each R.sup.20 and R.sup.21 group is independently selected from the group consisting of: hydrogen, methyl, ethyl, propyl, butyl, methoxy, ethoxy, propoxy, a C.sub.5 -C.sub.8 cycloalkyl, a C.sub.6 -C.sub.10 aryl, benzyloxy, naphthyloxy, a C.sub.2 -C.sub.10 alkenyl, diethylamino, dimethylamino, chlorine, bromine, morpholino, acetamido, and 2-furyl; and PA1 J is represented by formula (F17): ##STR11## wherein: each R.sup.5, R.sup.6, R.sup.7 and R.sup.8 group is independently hydrogen, halogen, a hydrocarbyl-containing group, or a heterocyclic group and wherein any two adjacent R.sup.5, R.sup.6, R.sup.7 and R.sup.8 groups may be connected to form a ring, preferably each R.sup.5, R.sup.6, R.sup.7 and R.sup.8 group is independently selected from the group consisting of: hydrogen, halogen, a C.sub.1 -C.sub.20 alkyl, a C.sub.1 -C.sub.20 alkoxy, a C.sub.3 -C.sub.18 cycloalkyl, a C.sub.6 -C.sub.18 aryl, a C.sub.6 -C.sub.18 aryloxy, a C.sub.6 -C.sub.18 hydroxyaryl, a C.sub.6 -C.sub.18 arylcarboxy, a C.sub.6 -C.sub.18 carboxyaryl, a C.sub.2 -C.sub.18 alkenyl, a C.sub.1 -C.sub.20 alkylamino, a C.sub.6 -C.sub.18 arylamino, a C.sub.6 -C.sub.18 aminoaryl, a C.sub.2 -C.sub.20 di(hydrocarbyl)amino, morpholino, alkylamido and wherein R.sup.5 and R.sup.6 or R.sup.7 and R.sup.8 may be connected to form a ring, for example, R.sup.5 and R.sup.6 or R.sup.7 and R.sup.8 may be joined by or be a --C.sub.4 H.sub.4 --, --(CH.sub.2).sub.3 --, or --C.sub.3 H.sub.3 N-- moiety; more preferably each R.sup.5, R.sup.6, R.sup.7 and R.sup.8 group is independently selected from the group consisting of: hydrogen, halogen, a C.sub.1 -C.sub.10 alkyl, a C.sub.1 -C.sub.10 alkoxy, a C.sub.5 -C.sub.8 cycloalkyl, a C.sub.6 -C.sub.10 aryl, a C.sub.6 -C.sub.18 aryloxy, a C.sub.2 -C.sub.10 alkenyl, a C.sub.1 -C.sub.10 alkylamino, a C.sub.6 -C.sub.18 arylamino, morpholino, acetamido and wherein R.sup.5 and R.sup.6 or R.sup.7 and R.sup.8 may be connected to form a 5 or 6 member ring; most preferably each R.sup.5, R.sup.6, R.sup.7 and R.sup.8 group is independently selected from the group consisting of: hydrogen, methyl, ethyl, propyl, butyl, methoxy, ethoxy, propoxy, a C.sub.5 -C.sub.8 cycloalkyl, a C.sub.6 -C.sub.10 aryl, benzyloxy, naphthyloxy, a C.sub.2 -C.sub.10 alkenyl, N,N-dialkylamino, N-alkyl-N-arylamino, chlorine, bromine, morpholino, acetamido and wherein R.sup.5 and R.sup.6 or R.sup.7 and R.sup.8 may be joined by or be a --C.sub.4 H.sub.4 --, --(CH.sub.2).sub.3 --, or --C.sub.3 H.sub.3 N-- moiety; and PA1 R.sup.23 is hydrogen, halogen, a hydrocarbyl-containing group, or a heterocyclic group, preferably R.sup.23 is a group selected from the group consisting of: hydrogen, a C.sub.1 -C.sub.20 alkyl, a C.sub.3 -C.sub.18 cycloalkyl, a C.sub.6 -C.sub.18 aryl, a C.sub.2 -C.sub.18 alkenyl, a C.sub.6 -C.sub.18 arylamino, and substituted sulfonyl, more preferably R.sup.23 is selected from the group consisting of hydrogen and --SO.sub.2 C.sub.6 H.sub.5. PA1 each R.sup.26 and R.sup.27 group is independently a --(CF.sub.2).sub.m F group wherein m is a number between 0 and 20, more preferably m is a number between 0 and 10, most preferably m is 0 or 1; and PA1 n is an integer preferably less than 5, more preferably n is 1 or 2. PA1 R.sup.30 is independently hydrogen, halogen, a hydrocarbyl-containing group, or a heterocyclic group, preferably R.sup.30 is a group independently selected from the group consisting of: hydrogen, halogen, a C.sub.1 -C.sub.20 alkyl, a C.sub.1 -C.sub.20 alkoxy, a C.sub.3 -C.sub.18 cycloalkyl, a C.sub.6 -C.sub.18 aryl, a C.sub.6 -C.sub.18 aryloxy, a C.sub.6 -C.sub.18 hydroxyaryl, a C.sub.6 -C.sub.18 arylcarboxy, a C.sub.6 -C.sub.18 carboxyaryl, a C.sub.2 -C.sub.18 alkenyl, a C.sub.1 -C.sub.20 alkylamino, a C.sub.6 -C.sub.18 arylamino, a C.sub.6 -C.sub.18 aminoaryl, a C.sub.2 -C.sub.20 di(hydrocarbyl)amino; more preferably R.sup.30 is a group independently selected from the group consisting of: hydrogen, halogen, a C.sub.1 -C.sub.10 alkyl, a C.sub.1 -C.sub.10 alkoxy, a C.sub.5 -C.sub.8 cycloalkyl, a C.sub.6 -C.sub.10 aryl, a C.sub.2 -C.sub.10 alkenyl, and a C.sub.1 -C.sub.10 alkylamino; and most preferably R.sup.30 is selected from the group consisting of: hydrogen, methyl, ethyl, propyl, butyl, methoxy, ethoxy, propoxy, a C.sub.5 -C.sub.8 cycloalkyl, and a C.sub.6 -C.sub.10 aryl; PA1 n is an integer preferably less than 5, more preferably n is 1 or 2. PA1 each R.sup.28 is independently hydrogen, a hydrocarbyl-containing group, or a heterocyclic group, preferably each R.sup.28 is independently selected from the group consisting of: hydrogen, a C.sub.1 -C.sub.20 alkyl, a C.sub.3 -C.sub.18 cycloalkyl, a C.sub.6 -C.sub.18 aryl, a C.sub.6 -C.sub.18 hydroxyaryl, a C.sub.6 -C.sub.18 carboxyaryl, a C.sub.2 -C.sub.18 alkenyl, a C.sub.6 -C.sub.18 aminoaryl; more preferably each R.sup.28 is independently selected from the group consisting of: hydrogen, a C.sub.1 -C.sub.10 alkyl, a C.sub.5 -C.sub.8 cycloalkyl, a C.sub.6 -C.sub.10 aryl, and a C.sub.2 -C.sub.10 alkenyl; PA1 n is an integer preferably less than 5, more preferably 1 or 2; and wherein PA1 M+ is selected from any suitable cation including sodium, triethylammonium and the like. PA1 R.sup.35 and R.sup.36 are as defined above for R.sup.33 and R.sup.34 ; PA1 X is O, S, or NR.sup.37 ; PA1 Y is N or CR.sup.38 ; PA1 R.sup.37 and R.sup.38 are as defined above for R.sup.33 ; and wherein PA1 M- is any suitable anion. PA1 R.sup.39 is independently hydrogen, a hydrocarbyl-containing group or a heterocyclic group, preferably R.sup.39 is a group selected from the group consisting of: hydrogen, a C.sub.1 -C.sub.20 alkyl, a C.sub.3 -C.sub.18 cycloalkyl, a C.sub.6 -C.sub.18 aryl, a C.sub.6 -C.sub.18 aryloxy, a C.sub.6 -C.sub.18 hydroxyaryl, a C.sub.6 -C.sub.18 arylcarboxy, a C.sub.6 -C.sub.18 carboxyaryl, a C.sub.2 -C.sub.18 alkenyl, a C.sub.1 -C.sub.20 alkylamino, a C.sub.6 -C.sub.18 arylamino, a C.sub.6 -C.sub.18 aminoaryl, a C.sub.2 -C.sub.20 di(hydrocarbyl)amino; PA1 R.sup.40 is independently hydrogen, halogen, a hydrocarbyl-containing group, or a heterocyclic group, preferably R.sup.40 is a group selected from the group consisting of: hydrogen, halogen, a C.sub.1 -C.sub.20 alkyl, a C.sub.1 -C.sub.20 alkoxy, a C.sub.3 -C.sub.18 cycloalkyl, a C.sub.6 -C.sub.18 aryl, a C.sub.6 -C.sub.18 aryloxy, a C.sub.6 -C.sub.18 hydroxyaryl, a C.sub.6 -C.sub.18 arylcarboxy, a C.sub.6 -C.sub.18 carboxyaryl, a C.sub.2 -C.sub.18 alkenyl, a C.sub.1 -C.sub.20 alkylamino, a C.sub.6 -C.sub.18 arylamino, a C.sub.6 -C.sub.18 aminoaryl, a C.sub.2 -C.sub.20 di(hydrocarbyl)amino, and carboxamide; PA1 X is C.dbd.R.sup.48, C(R.sup.38).sub.2, O, S, or NR.sup.37, more preferably X is C.dbd.R.sup.48, C(R.sup.38).sub.2 or S, wherein PA1 R.sup.37 is as defined above for R.sup.39, PA1 R.sup.38 is as defined above for R.sup.40, PA1 R.sup.48 is all oxo group, a divalent hydrocarbyl-containing group, or a divalent heterocyclic group, wherein R.sup.48 and R.sup.34 may be connected to form an unsaturated ring, for example, R.sup.48 and R.sup.34 may be joined by a --C.sub.3 H.sub.3 -- moiety, and wherein R.sup.37 and R.sup.34 may be connected to form a saturated or unsaturated ring; and wherein PA1 M- is any suitable anion. PA1 each R.sup.40, R.sup.41, R.sup.46 and R.sup.47 group is independently hydrogen, halogen, a hydrocarbyl-containing group, or a heterocyclic group, preferably each R.sup.40, R.sup.41, R.sup.46 and R.sup.47 group is independently selected from the group consisting of: hydrogen, a C.sub.1 -C.sub.20 alkyl, a C.sub.3 -C.sub.18 cycloalkyl, a C.sub.6 -C.sub.18 aryl, a C.sub.6 -C.sub.18 aryloxy, a C.sub.6 -C.sub.18 hydroxyaryl, a C.sub.6 -C.sub.18 arylcarboxy, a C.sub.6 -C.sub.18 carboxyaryl, a C.sub.2 -C.sub.18 alkenyl, a C.sub.1 -C.sub.20 alkylamino, a C.sub.6 -C.sub.18 arylamino, a C.sub.6 -C.sub.18 aminoaryl, a C.sub.2 -C.sub.20 di(hydrocarbyl)amino, wherein any two adjacent R.sup.41 to R.sup.43 groups may be connected to form a ring and wherein R.sup.44 and R.sup.45 may be connected to form a ring; more preferably R.sup.40, R.sup.41, R.sup.46 and R.sup.47 are methyl and R.sup.42 to R.sup.45 are hydrogen; PA1 n is an integer preferably less than 5, more preferably 1, 2 or 3; and wherein PA1 M- is any suitable anion. PA1 R.sup.2 is as defined above for Formula I, PA1 each R.sup.1 and R.sup.3 group is independently hydrogen, a hydrocarbyl-containing group, or a heterocyclic group, preferably R.sup.2 is hydrogen and each R.sup.1 and R.sup.3 is selected from the group consisting of hydrogen, a C.sub.1 -C.sub.20 alkyl, and a C.sub.1 -C.sub.20 alkylphenyl group, more preferably each R.sup.1 and R.sup.2 is hydrogen; PA1 j is a number having an average value between 0 and 25, more preferably j is a number having an average value between 5 and 15; PA1 k is a number having an average value between 0 and 100, more preferably k is a number having an average value of 0; and wherein PA1 the sum of j and k is at least 3.
A particularly preferred addition-cured silicone is formed by reacting (1) a multiply-vinyl-containing organopolysiloxane with (2) an organopolysiloxane containing a multiplicity of SiH bond per molecule (hereinafter "organohydropolysiloxane"). This reaction is typically facilitated by the presence of (3) a platinum catalyst of the Karstedt type. Platinum catalysts of the Karstedt type are described in U.S. Pat. Nos. 3,715,334, 3,775,452 and 3,814,730 which are herein incorporated by reference.
When vulcanizing silicones are used as modeling compounds (e.g., dental impression materials) it is customary to provide the compound to the user as two separate mixtures (i.e., the hydrosilation catalyst is stored separately from the hydrosilane crosslinker). When the user is ready to prepare an impression or model, the two parts will be mixed together, the silicone will be placed against the surface or object to be modeled and then the user will wait until the silicone completely cures. The cured silicone is then removed from the surface or object and retains a negative impression of that surface. A positive model may then be formed by filling the impression cavity with a material such as wax or plaster of Paris. In many instances it may not be feasible to form the positive model immediately. Therefore, it is also important that the impression retains its dimensional accuracy over a long period of time (often weeks or months).
The setting reaction of a vulcanizing silicone is triggered, in general, by the mixing together of the catalyst, crosslinker and polymer. By varying the amount of catalyst and crosslinker, the rate of setting may be adjusted. The rate of setting may be further adjusted by the incorporation of well known inhibitors and/or retarders. One such inhibitor is 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane. These retarders often operate by reacting competitively with the catalyst thereby slowing the crosslinking reaction. In general, with the slowing of the reaction both the working time and the setting time (as defined below) are affected.
As the material begins to set, its viscosity increases. Eventually, the mixture becomes "gelled" and is changed irreversibly into a crosslinked polymer or an "elastomer." At the gel-point the material no longer easily flows or adapts to new shapes. Therefore, in applications such as the taking of a dental impression this period of time defines the extent of the "working time" period.
When the reaction is complete (or "practically" complete) the material is said to be "set." This "setting time" is likewise an important parameter for a silicone impression material, as it is crucial that the material remain in contact with the surface it is to replicate until it has completely set. For dental impressions it is desirable to have a relatively short setting time (e.g., less than 10 minutes). Premature removal from the surface being replicated may result in a distorted impression which will continue to crosslink, in the distorted position, outside of the mouth. Unfortunately, this situation is often unnoticed by the dentist initially and is discovered only after an expensive, but worthless, dental appliance has been fabricated. The dentist and patient must then go through the entire lengthy impression making and appliance fabrication process again. This is a great expense and inconvenience.
For applications requiring detailed reproduction, such as dental impression materials, the setting time and the working time parameters are very important and must be carefully controlled. As previously mentioned, the working time measures the time period over which the reacting silicone material remains fluid enough to flow and change shape. After the reaction has reached the "gel point" the material's properties change drastically and resist further fluid flow. It is desirable to have sufficient working time so that the dentist may easily, and prior to gelation, (1) mix the materials and (2) place them in the mouth.
One major factor which affects both the working time and the setting time (in addition to the aforementioned use of an inhibitor or retarder) is the catalyst's "activity." Unfortunately, platinum catalysts of the Karstedt variety are somewhat sensitive to degradation and therefore are of variable activity. While the exact mechanism is presently unknown, this degradation may be advanced at high temperatures (such as might be encountered in a hot warehouse or in a truck-trailer). Over time the catalyst composition is believed to degrade and the setting time of the mixed composition becomes longer and longer. As previously mentioned even small changes in the setting time can have a detrimental effect on the accuracy of an impression if the user removes the material prior to its complete cure. Such early removal becomes more likely if the catalyst activity unexpectedly decreases upon storage. Another major factor which affects both the working time and the setting time is the ratio of catalyst to crosslinker. This ratio may be adjusted (purposely or inadvertently) by varying the amounts of each paste in the mix.
Various approaches have been attempted to provide an indication of a material's extent of cure. For example, U.S. Pat. Nos. 5,047,444; 5,118,559; and 5,182,316 describe curable compositions that can be monitored for extent of cure via detection of a UV fluorophore which is generated during the curing process. These compositions require the use of both a UV irradiation source and a UV fluorescence detector to monitor the extent of cure effectively and cannot be visualized by the naked eye. U.S. Pat. No. 3,509,081 describes the use, in a condensation silicone composition, of a dye that exhibits a visible color change at the desired degree of cure. This system is apparently limited and unpredictable, since, as the inventors state, it is "believed there is no technical relationship between the desired cure and the ultimate color change." In addition, as previously mentioned condensation silicones are limited by their dimensional instability. European Patent Application 0 492 830 A2 describes a method, for ultraviolet radiation curing compositions, of indicating a cure point by color change. Compositions of this invention comprise free-radical-curable materials, UV activated free-radical initiators, and a dye that changes color upon exposure to ultraviolet radiation in the presence of free-radical-generating photoinitiators. Preferred dyes of this invention include anthraquinone and bis-azo dyes. U.S. Pat. No. 4,788,240 discloses compositions comprising a polyorganosiloxane having two or more alkenyl radicals, a polyorganohydrogensiloxane, a platinum or platinum compound catalyst, and an anthraquinone or azo dye. The compositions are described as being useful as a molding or dental impression material. Materials exemplified in this patent require extended curing times which are undesirable for many dental procedures.